A triumphant Iraqi Prime Minister Haider al-Abadi declared on Monday that the coming year will see his forces defeat Islamic State of Iraq and Syria (ISIS) , after his military achieved its first major victory since collapsing in the face of the fighters 18 months ago.

Iraqi forces flew the national flag above the main government complex in Ramadi earlier in the day, declaring they had recaptured the city, a provincial capital west of Baghdad which fell to ISIS fighters in May.

“2016 will be the year of the big and final victory, when Daesh’s presence in Iraq will be terminated,” Abadi said in a speech broadcast on state television, using an Arabic acronym for ISIS that the hardline group rejects.

“We are coming to liberate Mosul and it will be the fatal and final blow to Daesh,” he added. Mosul, northern Iraq’s main city, is by far the largest population centre in the self-proclaimed caliphate Islamic State rules in Iraq and Syria.

The army’s apparent capture of Ramadi, capital of Anbar province in the Euphrates River valley west of Baghdad, marks a major milestone for U.S.-trained force that crumbled when ISIS fighters charged into Iraq in June 2014. In previous battles since then, Iraq’s armed forces operated mainly in a supporting role beside Iranian-backed Shi’ite militias.

Soldiers were shown on state television on Monday publicly slaughtering a sheep in an act of celebration.

Gunshots and an explosion could be heard as a state TV reporter interviewed other soldiers celebrating the victory with their automatic weapons held in the air. A separate plume of smoke could be seen nearby.

U.S. Army Colonel Steve Warren, a spokesman for a U.S.-led coalition backing Iraqi forces, said in a statement: “The clearance of the government centre is a significant accomplishment and is the result of many months of hard work.”

He said the coalition had provided more than 630 airstrikes in the area over the past six months as well as training, advice and equipment to the army, counter-terrorism forces and police.

The U.S.-led coalition, which includes major European and Arab powers, has been waging an air campaign against ISIS positions in both Iraq and Syria since a third of Iraqi territory fell to the fighters in mid-2014.

The Iraqi army was humiliated in that advance, abandoning city after city and leaving fleets of American armored vehicles and other weapons in the militants’ hands. One of the main challenges of the conflict since then has been rebuilding Iraq’s army into a force capable of capturing and holding territory.

Baghdad has said for months that it would prove its forces’ rebuilt capability by rolling back militant advances in Anbar, a mainly Sunni province encompassing the fertile Euphrates River valley from Baghdad’s outskirts to the Syrian border.

After encircling the provincial capital for weeks, Iraqi forces launched an assault to retake it last week and made a final push to seize the central administration complex on Sunday. Their progress had been slowed by explosives planted in streets and booby-trapped buildings.

Security officials said the forces still need to clear some pockets of insurgents in the city and its outskirts.

Keeping Control

Authorities gave no immediate death toll from the battle for the city. They have said most residents were evacuated before the assault.

Finance Minister Hoshiyar Zebari told Reuters the capture of Ramadi was “a done deal” but said the government had to do more to rebuild the city and encourage displaced people to return.

“The most important thing is to secure it (Ramadi) because Daesh can bounce back,” he said in an interview in Baghdad.

Iraq’s army took the lead in the battle for Ramadi, with the Shiite militias prominent in other campaigns held back from the battlefield to avoid antagonizing the mainly Sunni population. Washington had also expressed reluctance about being seen as fighting alongside the Iranian-backed groups.

Abadi took office in September 2014 after the ISIS advance, pledging to reconcile Iraq’s warring sectarian communities. While he initially swung behind Shiite militias to help halt ISIS’s onslaught, he has since tried to implement reforms to reduce the power of sectarian parties, angering many political leaders.

ISIS are ultra-hardline Sunnis who consider all Shiite Muslims to be apostates. They swept through northern and western Iraq in June 2014 and declared a “caliphate” to rule over all Muslims from territory in both Iraq and Syria, carrying out mass killings and imposing a draconian form of Sunni Islam.

Since then, the battle against the group in both Syria and Iraq has drawn in most global and regional powers, often with competing allies on the ground in complex multi-sided civil wars.

The Baghdad government says the next target after Ramadi is Mosul. Washington had hoped that a potentially decisive battle for that city would take place in 2015 but it was pushed back after the fighters seized Ramadi in May.

Abadi’s government plans to hand over Ramadi to local police and a Sunni tribal force once it is secured, to encourage Sunnis to resist ISIS.

Such a strategy would echo the U.S. military’s “surge” campaign of 2006-2007, which relied on recruiting and arming Sunni tribal fighters against a precursor of ISIS. Anbar, including Ramadi, was a major focus of that campaign at the height of the 2003-2011 U.S. war in Iraq.

U.S. and British reaction

Foreign Secretary Philip Hammond congratulated the Iraqi government after the national flag was raised over Ramadi once it was liberated.

“This is the latest in a series of significant losses for Daesh. These barbaric terrorists have lost 30 percent of the territory they once held in Iraq,” Hammond said in a statement.

“They have been driven out of cities across the country by Iraqi forces, with support from the UK and the global coalition.”

The United States also welcomed the Iraqi forces' victory. “We commend the government of Iraq and the brave Iraqi forces who have displayed such tremendous perseverance,” State Department spokesman Mark Toner said.